Eccentric drives for portable handheld work apparatus are known wherein a wheel, especially a toothed wheel, is driven by a drive motor. An eccentric cam is fixed on an end face of the wheel and the cam is connected to a drive rod. Roller bodies are arranged radially between the cam and the eye of the connecting rod. The roller bodies are held axially by the circular disc-shaped edges of the connecting rod eye. The roller bodies can drop out of the eye of the connecting rod toward the center during assembly or during maintenance work as long as the connecting rod is not seated on the cam. Especially the assembly of the connecting rod is made more difficult thereby.
It is an object of the invention to provide an eccentric drive which is easy to assembly and to disassemble.
The eccentric drive of the invention includes an eccentric drive for a handheld portable work apparatus. The eccentric drive of the invention includes: a wheel defining a rotational axis and having an end face; a cam fixedly mounted eccentrically on the end face so as not to be rotatable relative to the wheel; a drive motor for driving the wheel to rotate about the rotational axis; a connecting rod having a connecting rod eye for receiving the cam therein so as to cause the connecting rod eye and the cam to conjointly define an interface therebetween; a plurality of roller bodies disposed at the interface to define a roller bearing between the cam and the connecting rod eye; the wheel having an annular slot disposed in surrounding relationship to the cam; each of the roller bodies having a first axial end engaging the annular slot; a holder having an edge and being fixed on the cam; each of the roller bodies having a second axial end adjacent the holder; and, the roller bodies projecting radially beyond the edge of the holder.
An advantage of the invention is that an eccentric drive, especially for a portable handheld work apparatus, is provided which can be assembled and disassembled rapidly and without difficulty and without additional complexity with respect to components. According to the invention, an annular slot surrounding the cam is provided in which the roller bodies engage with their axial ends and, with their other axial ends, lie against a holding element fixed on the cam. In this way, the roller bodies cannot drop out of their position when the connecting rod is assembled onto the cam and disassembled therefrom. The roller bodies project in the radial direction beyond the edge of the holding element. In this way, a roller bearing is formed on the cam over which the connecting rod can be axially passed with the connecting rod eye without the roller bodies moving out of their position. The roller bodies are inseparably held on the wheel around the cam. The depth of the annular slot is greater than the spacing between the holding element and the adjacent axial ends of the roller bodies.
In a preferred embodiment, the width of the annular slot (in which the roller bodies axially engage) is greater than the diameter of the roller bodies so that the roller bodies are inseparably held in the slot with radial play. The holding element is preferably formed to have a circular shape and is fixed to the end face of the cam. The holding element is preferably formed as a ring or disc. The outer diameter of the ring is less than the outer diameter of the roller bearing. The holding element is preferably made of spring steel and is fixed to the end face of the cam with a spot-weld connection. It can be practical to bring the connecting rod in sliding contact engagement with the end face of the wheel in order to hold the structural elevation of the eccentric drive low. The end face of the wheel defines a lateral stop for the connecting rod. Preferably, the wheel is configured as a toothed wheel and the cam is configured as one piece with the toothed wheel. The toothed wheel is in meshing engagement with a pinion driven by the drive motor.